A study on the effects of magnetohydrodynamic perturbations on nonthermal beam formation during the current decay phase of disruptions in the T-10 tokamak

Abstract

Repetitive bursts of nonthermal (Eγ ∼ 15 − 150 keV) x-ray radiation are observed during the plasma current decay phase of the density limit disruptions in the T-10 tokamak. The repetition rate of the nonthermal bursts correlates with the current decay rate. Analysis indicates that the phenomena can be connected with the nonthermal electrons initiated during the abrupt growth of the magnetohydrodynamic (MHD) modes in the series of minor disruptions. Application of the electron cyclotron waves in the post energy quench plasma allows control of the bursting MHD modes and prevention of nonthermal beam formation. Phenomenological modelling indicates that prevention of the nonthermal beams can be connected with elimination of the electric fields induced during magnetic reconnection in the series of minor disruptions, and reduction of the ‘equilibrium’ longitudinal electric field during auxiliary plasma heating.